The Potrillo volcanic field is a broad monogenetic volcanic region on the Rio Grande Rift in southern New Mexico and northern Chihuahua, made up of many vents, cones, maars, and lava flows rather than a single mountain. Its three main parts include the large, older West Potrillo field, the younger Aden–Afton field, and the Black Mountain–Santo Tomas alignment near the Rio Grande. Eruptions here span from hundreds of thousands of years ago to much younger lava at Aden. The area is especially important because maars such as Kilbourne Hole brought up upper mantle and lower crust rocks, and Aden Crater yielded an 11,000-year-old ground sloth skeleton with preserved skin and hair.